The present invention relates to an electronically controlled fuel injection device which is used to supply fuel to an internal combustion engine (hereafter referred to simply as an engine, and more particularly to an electronically controlled fuel injection device used in engines that are mounted in two-wheeled vehicles and the like.
Conventionally, electronically controlled fuel injection devices which control the fuel injection timing and amount of injection, i.e., injection period or the like, by means of an electronic circuit have been employed in four-cycle gasoline engines mounted in automobiles and the like, and especially in multi-cylinder gasoline engines with 4, 6 or 8 cylinders which have a relatively large total displacement of approximately 1000 cc to 4000 cc, from the standpoint of improving fuel economy in response to exhaust gas regulations, or from the standpoint of improving the operating characteristics.
For example, FIG. 23 shows a known electronically controlled fuel injection device. This device is a port injection type device which injects fuel toward an intake port of an engine 1 by means of an electromagnetic valve type injector 3 which is attached at an inclination toward the downstream side with respect to an intake passage inside the intake manifold 2 of the engine 1. In this port injection type electronically controlled fuel injection device, as is shown in FIG. 23, fuel (gasoline) inside a fuel tank 4 is fed out under pressure by an in-tank fuel pump 5 accommodated inside the fuel tank 4, e.g., a centrifugal flow type fuel pump. This fuel is supplied to the injector 3 via a highly pressure-resistant fuel feed pipe 7 and a delivery pipe (not shown) after passing through a high-pressure filter 6 at an intermediate point.
Furthermore, the fuel conducted by the fuel feed pipe 7 is also fed into a fuel pressure regulator 8, and the excess fuel (i.e., the fuel not injected from the injector 3) is returned to the fuel tank 4 via a fuel return pipe 9. As a result, the pressure of the fuel upstream of the injector 3 (i.e., the fuel pressure) is maintained at a specified high pressure value. Thus, since the pressure of the fuel is maintained at a high pressure, the generation of vapor in the case of high temperatures or the like is suppressed; furthermore, the fuel that is injected from the injector 3 can be finely atomized.
Furthermore, in order to detect the conditions of the engine 1 in an appropriate manner, this electronically controlled fuel injection device is equipped with an engine rotational speed sensor 10, a water temperature sensor 11, an O2 sensor 12, an intake pressure sensor 13, a throttle sensor 14, and air flow rate sensor 15, an intake temperature sensor 16 and the like. On the basis of operating information concerning the engine 1 that is detected by these sensors, a control unit (ECU) 17 that is equipped with an electronic circuit calculates the current optimal fuel injection amount, i.e., the fuel injection time and fuel injection timing, and transmits this information to the injector 3. As a result, the injection time and injection timing of the fuel from the injector 3 are optimally controlled in accordance with the operating conditions of the engine 1.
Meanwhile, in the case of engines with a relatively small displacement that are mounted in two-wheeled vehicles or comparable vehicles, or in other engine-driven devices, e.g., engines with a displacement of approximately 50 cc to 250 cc per cylinder, fuel injection devices using carburetors or the like that control the amount of fuel injection by means of pressure have been employed in the past, one reason being that exhaust gas regulations and the like were not too strict for such engines.
However, as a recent step in the prevention of global warming and environmental protection, fine control of combustion for the purpose of reducing emissions of carbon dioxide, hydrocarbons and the like by reducing fuel consumption has become necessary even in such engines with a small displacement.
When an attempt is made to achieve optimal fuel injection in the same manner as in large-displacement automobile engines by using systems similar to existing electronically controlled fuel injection devices instead of conventional carburetors, the following problems arise.
First of all, in the case of an electronically controlled fuel injection device using a conventional fuel pump 5 and injector 3, either time or area is used as a control parameter in controlling the amount of fuel injection and the like. Accordingly, the flexibility of control, i.e., the control range, is narrow, so that such devices are undesirable in the case of engines mounted in two-wheeled vehicles and the like, in which it is necessary to perform optimal control of the combustion while giving serious consideration to the operating performance from the standpoint of the application involved.
Secondly, conventional fuel pumps 5 are centrifugal flow type fuel pumps, and have a relatively large and complicated structure equipped with pump parts, motor parts and the like. Furthermore, an in-tank installation system in which the fuel pump is disposed inside the fuel tank 4 is generally employed; as a result, for example, it is difficult to fit such a fuel pump in a two-wheeled vehicle engine in which there are restrictions on the size and shape of the fuel tank.
Third, since the fuel feed pipe 7 extending from the fuel pump 5 to the injector 3 is filled with high-pressure fuel, such a system is undesirable from the standpoint of safety in the case of engines mounted in two-wheeled vehicles, in which accidental spills (i.e., accidents in which two-wheeled vehicles are laid down) and the like must be taken into consideration.
Fourth, in the case of conventional systems which supply fuel at a high pressure, the electric power consumption of the fuel pump 5 itself is large; furthermore, it is necessary to circulate fuel at a high flow rate via the fuel pressure regulator 8. As a result, the overall electric power consumption is increased even further. Accordingly, such systems are undesirable for engines mounted in two-wheeled vehicles and the like, in which there is a need to reduce the electric power consumption.
Fifth, in the case of conventional systems which supply fuel at a high pressure, a high pressure resistance is required, so that such systems are generally expensive, including the cost of the materials of the constituent parts, the cost of high quality control during manufacture and the like. Accordingly, such systems are undesirable for engines mounted in two-wheeled vehicles, in which there is a demand for cost reduction.
The present invention was devised in light of the above-mentioned problems encountered in the prior art. It is an object of the present invention to provide an electronically controlled fuel injection device which makes it possible to achieve an optimal combustion state by means of precise control such that exhaust gas countermeasures are also performed while maintaining the operating performance in a small-displacement engine, e.g., an engine mounted in a two-wheeled vehicle or the like, and at the same time achieving a reduction in electric power consumption, a reduction in cost, a reduction in size and a reduction in the installation space required.
The first electronically controlled fuel injection device of the present invention is an electronically controlled fuel injection device which injects fuel into the intake passage of an engine, comprising a volume type (i.e., positive displacement) electromagnetically driven pump which uses electromagnetic force as a driving source, and which pressure-feeds fuel conducted from the fuel tank, an inlet orifice nozzle which has an orifice part that allows the passage of the fuel that is pressure-fed by this electromagnetically driven pump, an outlet orifice nozzle which has an orifice part that allows the passage of fuel so that a specified amount of the fuel that has passed through the inlet orifice nozzle is circulated back to the fuel tank, an injection nozzle which injects an amount of fuel equal to the difference between the fuel that has passed through the inlet orifice nozzle and the fuel that has passed through the outlet orifice nozzle into the intake passage, and a control arrangement for controlling the electromagnetically driven pump in response to the engine cycle.
In this construction, when a specified driving signal is sent to the electromagnetically driven pump by the control arrangement, the electromagnetically driven pump is actuated by the electromagnetic force that is generated, so that a specified amount of fuel is pressure-fed. Then, the pressure-fed fuel passes through the inlet orifice nozzle and is adjusted to a flow rate (pressure) that corresponds to the driving signal, and a portion of the fuel that flows out from this inlet orifice nozzle passes through the outlet orifice nozzle and is circulated back into the fuel tank. Furthermore, an amount of fuel equal to the difference between the fuel that has passed through the inlet orifice nozzle and the fuel that has passed through the outlet orifice nozzle is injected into the intake passage from the injection nozzle.
Here, the inlet orifice nozzle acts as a sensor that detects the fuel flow rate by the pressure difference before and after the inlet orifice nozzle; furthermore, the outlet orifice nozzle acts to apply a bias to the flow rate through the inlet orifice nozzle, so that the region of strong nonlinearity of the small-flow-rate region is not used in the flow rate characteristics of the inlet orifice nozzle.
In the above-mentioned construction, the electromagnetically driven pump may comprise a cylindrical body (plunger-receiving body) that forms a fuel passage, a plunger which is disposed in tight contact with the inside of the passage of this cylindrical body so that the plunger is free to undergo reciprocating motion within a specified range, and which has a fuel passage that passes through in the direction of the reciprocating motion, a first check valve which is urged so that the fuel passage of the plunger is blocked, and which is disposed so that the fuel passage is opened by the movement of the plunger in one direction, an elastic body which is supported on the cylindrical body, and which urges the plunger in the direction of the reciprocating motion, a second check valve which is disposed on the downstream side of the plunger with respect to the direction of flow of the fuel, and which is urged so that the passage of the cylindrical body is blocked, and disposed so that that the passage of the cylindrical body is opened by the movement of the plunger in the other direction, and a solenoid coil which applies an electromagnetic force to the plunger.
In this construction, when the plunger is caused to begin an advancing motion (in the above-mentioned second direction) by the exciting action of the solenoid coil from the resting position in which the plunger is held in a specified position inside the cylindrical body by the elastic body, the second check valve opens the passage of the cylindrical body, so that fuel is pressure-fed toward the inlet orifice nozzle. On the other hand, when the plunger that has reached a specified position begins a return motion (in the above-mentioned first direction), the second check valve blocks the passage of the cylindrical body, and at the same time, the first check valve opens the fuel passage of the plunger, so that fuel is sucked in behind the plunger, i.e., toward the downstream side. Thus, fuel at a specified pressure is pressure-fed toward the inlet orifice nozzle by the reciprocating action of the plunger.
Furthermore, the second electronically controlled fuel injection device of the present invention is an electronically controlled fuel injection device which injects fuel into the intake passage of the engine, comprising a volume type (i.e. positive displacement) electromagnetically driven pump which uses electromagnetic force as a driving source, and which pressure-feeds fuel conducted from the fuel tank, a circulation passage which circulates fuel that has been pressurized to a specified pressure or greater in a specified initial stage of the pressure-feeding stroke performed by the electromagnetically driven pump back into the fuel tank, a valve body which blocks the circulation passage in the later stage of the pressure-feeding stroke but not the initial stage, an inlet orifice nozzle which has an orifice part that allows the passage of fuel pressurized to a specified pressure in the later stage of the pressure-feeding stroke, an outlet orifice nozzle which has an orifice part that allows the passage of fuel so that a specified amount of the fuel that has passed through the inlet orifice nozzle is circulated back into the fuel tank, an injection nozzle which injects an amount of fuel equal to the difference between the fuel that has passed through the inlet orifice nozzle and the fuel that has passed through the outlet orifice nozzle into the intake passage, and a control arrangement for controlling the electromagnetically driven pump in response to the engine cycle.
In this construction, fuel mixed with vapor which is pressurized to a specified pressure or greater in the initial stage of the pressure-feeding stroke performed by the electromagnetically driven pump is circulated back into the fuel tank via the circulation passage. Furthermore, in the later stage of the pressure-feeding stroke, the valve body blocks the circulation passage, so that the pressure of the fuel is elevated to a specified pressure, and the fuel passes through the inlet orifice nozzle and is adjusted (metered) to a flow rate (pressure) that corresponds to the driving signal. Then, a portion of the fuel that has flowed out from this inlet orifice nozzle passes through the outlet orifice nozzle and is circulated back to the fuel tank. Meanwhile, an amount of fuel equal to the difference between the fuel that has passed through the inlet orifice nozzle and the fuel that has passed through the outlet orifice nozzle is injected into the intake passage from the injection nozzle. Thus, since the fuel mixed with vapor is circulated back to the fuel tank before being metered by the inlet orifice nozzle, the control of the amount of fuel injected is stabilized, especially at high temperatures.
Furthermore, the third electronically controlled fuel injection device of the present invention is an electronically controlled fuel injection device which injects fuel into the intake passage of the engine, comprising a positive displacement electromagnetically driven pump which uses electromagnetic force as a driving source, and which pressure-feeds fuel conducted from the fuel tank, a circulation passage which circulates fuel that has been pressurized to a specified pressure or greater in a specified initial stage of the pressure-feeding stroke performed by the electromagnetically driven pump back into the fuel tank, a valve body which blocks the circulation passage in the later stage of the pressure-feeding stroke but not the in the initial stage, an inlet orifice nozzle which has an orifice part that allows the passage of fuel pressurized to a specified pressure in the later stage of the pressure-feeding stroke, an injection nozzle which injects the fuel that has passed through the inlet orifice nozzle into the intake passage in cases where the pressure of the fuel is equal to or greater than a specified pressure, and a control arrangement for controlling the electromagnetically driven pump in response to the engine cycle.
In this construction, fuel mixed with vapor which is pressurized to a specified pressure or greater in the initial stage of the pressure-feeding stroke performed by the electromagnetically driven pump is circulated back into the fuel tank via the circulation passage. Furthermore, in the later stage of the pressure-feeding stroke, the valve body blocks the circulation passage, so that the pressure of the fuel is elevated to a specified pressure, and the fuel passes through the inlet orifice nozzle and is adjusted (metered) to a flow rate (pressure) that corresponds to the driving signal. Then, when the fuel that has flowed out from this inlet orifice nozzle reaches a specified pressure or greater, this fuel is injected into the intake passage from the injection nozzle. Thus, since the fuel mixed with vapor is circulated back to the fuel tank before being metered by the inlet orifice nozzle, the control of the amount of fuel injected is stabilized, especially at high temperatures.
In both of the above-mentioned constructions, a construction may be employed in which the electromagnetically driven pump has a cylindrical body that forms a fuel passage, a plunger which is disposed in tight contact with the inside of the passage of the cylindrical body so that the plunger is free to undergo a reciprocating motion within a specified range, and which sucks in fuel by moving in one direction and pressure-feeds this sucked-in fuel by moving in the other direction, an elastic body which urges the plunger in the direction of the reciprocating motion, an outlet check valve which opens a fuel passage that communicates with the inlet orifice nozzle when the fuel that is pressure-fed by the plunger reaches a specified pressure or greater, and a solenoid coil which applies an electromagnetic force to the plunger; the above-mentioned circulation passage is formed so that this passage passes through the above-mentioned plunger in the direction of the reciprocating motion of the plunger, and a pressurizing valve is provided which is urged so that this valve blocks the circulation passage, and which opens when the pressure-fed fuel reaches a specified pressure or greater; and the above-mentioned valve body consists of a spill valve which is disposed in a manner that allows this valve to undergo reciprocating motion in the direction of the reciprocating motion of the plunger, so that the circulation passage is opened in the initial stage of the pressure-feeding stroke and blocked in the later stage of the pressure-feeding stroke, and so that the outlet check valve is opened at an intermediate point in this later stage.
Furthermore, in both of the above-mentioned constructions, a construction may be employed in which the electromagnetically driven pump has a cylindrical body that forms a fuel passage, a plunger which is disposed in tight contact with the inside of the passage of the cylindrical body so that the plunger is free to undergo reciprocating motion within a specified range, and which sucks in fuel by moving in one direction and pressure-feeds this sucked-in fuel by moving in the other direction, an elastic body which urges the plunger in the direction of the reciprocating motion, an outlet check valve which opens a fuel passage that communicates with the inlet orifice nozzle when the fuel that is pressure-fed by the plunger reaches a specified pressure or greater, and a solenoid coil which applies an electromagnetic force to the plunger; the above-mentioned circulation passage is formed on the outside of the cylindrical body; a pressurizing valve which is driven so that this valve blocks the circulation passage, and which opens the circulation passage when the fuel that is pressure-fed by the plunger reaches a specified pressure or greater, is installed on the circulation passage; a spill port which communicates with the circulation passage is formed in the above-mentioned cylindrical body; and the above-mentioned valve body is constituted by of the above-mentioned plunger, which opens the spill port in the initial stage of the pressure-feeding stroke, and closes the spill port in the later stage of the pressure-feeding stroke.
In this construction, when the fuel that is sucked in in the initial stage of the pressure-feeding stroke performed by the plunger reaches a specified pressure or greater, the pressurizing valve opens the circulation passage that is formed on the outside of the cylindrical body, so that fuel mixed with vapor flows out from the spill port formed in the side wall of the cylindrical body, and is circulated back to the fuel tank. Then, when the plunger moves further and enters the later stage of the pressure-feeding stroke, (the outer circumferential surface of) the plunger blocks the spill port, and the fuel is further pressurized. Then, when the fuel is pressurized to a specified pressure or greater, the outlet check valve opens the fuel passage, so that the pressurized fuel passes through the inlet orifice nozzle.
In the constructions of the above-mentioned second and third electronically controlled fuel injection devices, a construction may be employed in which the circulation passage is formed so that the fuel is circulated in the opposite direction from the direction of injection of the fuel by the injection nozzle.
In this construction, since circulation is performed in the opposite direction from the direction of injection of the fuel, the vapor that is mixed with the fuel can be positively expelled. Especially in cases where the injection direction is oriented substantially downward in the vertical direction, the circulation direction is oriented substantially upward in the vertical direction; accordingly, the vapor is positively expelled by buoyancy.
In the constructions of the above-mentioned first and second electronically controlled fuel injection devices, a construction may be employed in which the injection nozzle has a cylindrical body (valve-receiving body) which demarcates a fuel passage that communicates with the above-mentioned inlet orifice nozzle and outlet orifice nozzle, a valve body which is disposed so that this valve body is free to undergo reciprocating motion inside the cylindrical body, and which opens and closes the fuel injection passage, and an urging spring which urges the valve body by means of a specified urging force so that the fuel injection passage is blocked.
In this construction, fuel at a specified pressure flows into the cylindrical body from the inlet orifice nozzle; meanwhile, fuel at a specified flow rate flows out from the outlet orifice nozzle and is circulated back into the fuel tank. Here, when the fuel that flows in from the inlet orifice nozzle increases so that the pressure inside the cylindrical body is increased, the valve body moves against the urging force of the urging spring and opens the injection passage, so that fuel is injected from the injection nozzle. As a result, the pressure inside the cylindrical body is maintained at a constant value. Specifically, an amount of fuel equal to the difference between the fuel that has flowed in from the inlet orifice nozzle and the fuel that has flowed out from the outlet orifice nozzle is injected from the injection nozzle as injected fuel.
In the construction of the above-mentioned third electronically controlled fuel injection device, a construction may be employed in which the injection nozzle has a cylindrical body which demarcates a fuel passage that conducts fuel that has flowed in from the inlet orifice nozzle, a valve body which is disposed so that this valve body is free to undergo reciprocating motion inside the cylindrical body, and which opens and closes the fuel injection passage, and an urging spring which urges the valve body by means of a specified urging force so that the fuel injection passage is blocked.
In this construction, fuel at a specified pressure flows into the cylindrical body from the inlet orifice nozzle, and when the pressure inside this cylindrical body further rises to a specified pressure, the valve body moves against the urging force of the urging spring and opens the injection passage, so that fuel is injected from the injection nozzle.
In the above-mentioned construction, a construction may be employed in which an assist air passage that allows the passage of assist air used to assist in the atomization of the injected fuel is formed in the injection nozzle.
In this construction, when fuel is injected from the injection nozzle, air that is caused to jet through the assist air passage agitates the injected fuel so that atomization of the injected fuel is promoted.
Furthermore, in the above-mentioned construction, a construction may be employed in which an adjustment mechanism for adjusting the urging force of the urging spring is installed in the injection nozzle.
In this construction, the opening pressure (relief pressure) of the valve body is adjusted to the desired value by appropriately adjusting the urging force of the urging spring using the adjustment mechanism.
In the constructions of the above-mentioned first and second electronically controlled fuel injection devices, a construction may be employed in which a back-flow preventing valve which prevents back flow in the fuel passage is installed in the injection nozzle.
In this construction, the pressure of the fuel inside the fuel passage on the upstream side of the back-flow preventing valve is raised and maintained at a specified value, so that the generation of vapor is suppressed. Furthermore, the back flow of vapor conducted toward the outlet orifice nozzle on the downstream side from the fuel passage is prevented, so that the discharge of vapor is efficiently performed.
In the above-mentioned construction, a construction may also be employed in which an adjuster that adjusts the opening pressure of the above-mentioned back-flow preventing valve is installed in the injection nozzle.
In this construction, the opening pressure of the back-flow preventing valve is adjusted to an appropriate desired value by adjusting the adjuster.
In the constructions of the above-mentioned first and second electronically controlled fuel injection devices, a construction may be employed in which a fuel passage that communicates with the inlet orifice nozzle and outlet orifice nozzle is formed in the injection nozzle as a passage that passes through the vicinity of the injection passage that is opened and closed by the valve body, and allows fuel to flow in one direction.
In this construction, the fuel that has flowed in from the inlet orifice nozzle is conducted to the vicinity of the injection passage that is opened and closed by the valve body, and is injected as necessary; furthermore, the fuel that is not injected flows toward the outlet orifice nozzle on the downstream side. Thus, as a result of the fuel forming a one-way flow, the accumulation of vapor is prevented; furthermore, the injection nozzle is cooled by the fuel.
In the above-mentioned construction, a construction may be employed in which the electromagnetically driven pump and injection nozzle are joined as an integral unit.
In this construction, the electromagnetically driven pump and injection nozzle are treated as a single module as in conventional injectors; this contributes to convenience in terms of handling.
In the above-mentioned construction, at least two characteristics, i.e., the current that flows through the solenoid coil of the electromagnetically driven pump and the time for which this current flows, are used as control parameters for the control arrangement.
In this construction, at least two characteristics, i.e., the current that flows through the solenoid coil, i.e., the pressure of the fuel into which this current is converted via the electromagnetic force, and the time for which this current flows, are used as control parameters; accordingly, compared to conventional single-element control using time only, a desired precise fuel injection pattern can be formed; furthermore, the control width is increased, and the transient response characteristics are also advantageous.
In the construction of the above-mentioned third electronically controlled fuel injection device, a construction may be employed in which the control arrangement uses only the time for which current is caused to flow through the electromagnetically driven pump as a control parameter.
In this construction, a pressure-feeding operation of fuel from which vapor has been expelled beforehand by the plunger is performed by causing a predetermined current to flow for a specified period of time, so that fuel at a relatively high pressure passes through the inlet orifice nozzle. Accordingly, the inlet orifice nozzle can be used in a region of good linearity. Furthermore, the fuel that is metered by being passed through the inlet orifice nozzle is further raised to a specified pressure so that the valve body opens the injection passage and fuel is injected.
In the constructions of the above-mentioned first and second electronically controlled fuel injection devices, a construction may be used in which the control arrangement drives the electromagnetically driven pump by superimposed driving in which an auxiliary pulse that is smaller than a specified level is superimposed on a fundamental pulse consisting of a current of this specified level.
In this construction, when the electromagnetically driven pump is driven, the pump is driven with an auxiliary pulse superimposed on the fundamental pulse; accordingly, the amount of fuel that is circulated from the outlet orifice nozzle is increased, and the admixed vapor is efficiently expelled.
Furthermore, in the above-mentioned construction, the control arrangement may cause the solenoid coil to be powered at least during the pressure-feeding stroke of the plunger that forms a part of the electromagnetically driven pump.
In this construction, the plunger is caused to initiate the pressure-feeding operation by the excitation of the solenoid coil so that fuel is discharged. Here, the amount of fuel that is discharged and the mixing conditions (uniform mixing or non-uniform mixing) can be precisely controlled by appropriately adjusting the current that is passed through in this case and the time for which this current is passed through.